TY - JOUR
T1 - Crystal structure of LeuA from <em>Mycobacterium tuberculosis</em>, a key enzyme in leucine biosynthesis
JF - Proceedings of the National Academy of Sciences of the United States of America
JO - Proc Natl Acad Sci U S A
SP - 8295
LP - 8300
DO - 10.1073/pnas.0400820101
VL - 101
IS - 22
AU - Koon, Nayden
AU - Squire, Christopher J.
AU - Baker, Edward N.
Y1 - 2004/06/01
UR - http://www.pnas.org/content/101/22/8295.abstract
N2 - The leucine biosynthetic pathway is essential for the growth of Mycobacterium tuberculosis and is a potential target for the design of new anti-tuberculosis drugs. The crystal structure of α-isopropylmalate synthase, which catalyzes the first committed step in this pathway, has been determined by multiwavelength anomalous dispersion methods and refined at 2.0-Å resolution in complex with its substrate α-ketoisovalerate. The structure reveals a tightly associated, domain-swapped dimer in which each monomer comprises an (α/β)8 TIM barrel catalytic domain, a helical linker domain, and a regulatory domain of novel fold. Mutational and crystallographic data indicate the latter as the site for leucine feedback inhibition of activity. Domain swapping enables the linker domain of one monomer to sit over the catalytic domain of the other, inserting residues into the active site that may be important in catalysis. The α-ketoisovalerate substrate binds to an active site zinc ion, adjacent to a cavity that can accommodate acetyl-CoA. Sequence and structural similarities point to a catalytic mechanism similar to that of malate synthase and an evolutionary relationship with an aldolase that catalyzes the reverse reaction on a similar substrate.
ER -